"Maximum Number of Bonds" Definition
The International Union of Pure and Applied Chemistry (IUPAC) has made several attempts to arrive at an unambiguous definition of valence. The current version, adopted in 1994,:
- The maximum number of univalent atoms (originally hydrogen or chlorine atoms) that may combine with an atom of the element under consideration, or with a fragment, or for which an atom of this element can be substituted.
Hydrogen and chlorine were originally used as examples of univalent atoms, because of their nature to form only one single bond. Hydrogen has only one valence electron and can form only one bond with an atom that has an incomplete outer shell. Chlorine has seven valence electrons and can form only one bond with an atom that donates a valence electron to complete chlorine's outer shell. However, chlorine can also have oxidation states from +1 to +7 and can form more than one bond by donating valence electrons.
Although hydrogen has only one valence electron, it can form bonds with more than one atom in hypervalent bonds. In the bifluoride ion (−), for example, it forms a three-center four-electron bond with two fluoride atoms:
Another example is the Three-center two-electron bond in diborane (B2H6).
Read more about this topic: Valence (chemistry)
Famous quotes containing the words maximum, number, bonds and/or definition:
“Only at his maximum does an individual surpass all his derivative elements, and become purely himself. And most people never get there. In his own pure individuality a man surpasses his father and mother, and is utterly unknown to them.”
—D.H. (David Herbert)
“The growing good of the world is partly dependent on unhistoric acts; and that things are not so ill with you and me as they might have been, is half owing to the number who lived faithfully a hidden life, and rest in unvisited tombs.”
—George Eliot [Mary Ann (or Marian)
“We black women must forgive black men for not protecting us against slavery, racism, white men, our confusion, their doubts. And black men must forgive black women for our own sometimes dubious choices, divided loyalties, and lack of belief in their possibilities. Only when our sons and our daughters know that forgiveness is real, existent, and that those who love them practice it, can they form bonds as men and women that really can save and change our community.”
—Marita Golden, educator, author. Saving Our Sons, p. 188, Doubleday (1995)
“According to our social pyramid, all men who feel displaced racially, culturally, and/or because of economic hardships will turn on those whom they feel they can order and humiliate, usually women, children, and animals—just as they have been ordered and humiliated by those privileged few who are in power. However, this definition does not explain why there are privileged men who behave this way toward women.”
—Ana Castillo (b. 1953)